Compliant printer blade for facsimile printer

ABSTRACT

An improved printing blade for a facsimile printer of the drum type is made out of a thin strip of stainless steel. The blade is inserted into a rigid blade carrier and locked firmly in place by a spring-biased eccentric locking roller. The carrier is mounted on the printer in such a position as to cause the edge of the blade to bear against web material over a helical wire on the printer drum with sufficient force to maintain the blade against the web material. The inherent resilience of the blade is sufficient to compensate for any differences in the radius of the helical wire from the axis of the turning drum and differences in the thicknesses of web material being passed between the drum and the blade.

United States Patent [191 Hauser [4 1 Nov. 18, 1975 COMPLIANT PRINTERBLADE FOR FACSIMILE PRINTER [75] Inventor: Frank W. Hauser, SantaMonica,

Calif.

[22] Filed: Mar. 11, 1974 [21] Appl. No.: 449,738

[52] US. Cl. 346/73 E; 346/139 C [51] Int. C1. G03G 17/02; GOlD 15/06[58] Field of Search 346/74 E, 74 CH, 74 S, 346/74 SB, 139 C; 178/6.6 A

[56] 9 References Cited UNITED STATES PATENTS 2,505,779 5/1950 Long346/74 EL 2,621,999 12/1952 Alden 346/74 EL 3,491,365 1/1970 DeSautels346/74 EL 3,546,707 12/1970 Dixon 346/74 EL 4/1974 Andree .1

Primary Examiner-Bernard Konick Assistant Examiner-Jay P. LucasAttorney, Agent, or FirmLindenberg, Freilich, Wasserman, Rosen &-Fernandez 57 ABSTRACT An improved printing blade for a facsimile printerof the drum type is made out of a thin strip of stainless steel. Theblade is inserted into a rigid blade carrier and locked firmly in placeby a spring-biased eccentric locking roller. The carrier is mounted onthe printer in such a position as to cause the edge of the blade to bearagainst web material over a helical wire on the printer drum withsufficient force to maintain the blade against the web material. Theinherent resilience of the blade is sufficient to compensate for anydifferences in the radius of the helical wire from the axis of theturning drum and differences in the thicknesses of web material beingpassed between the drum and the blade.

2 Claims, 5 Drawing Figures US. Patent Nov. 18, 1975 Sheet10f2 3,921,181

Sheet 2 of 2 US. Patent COMPLIANT PRINTER BLADE FOR FACSIMILE PRINTERBACKGROUND OF THE INVENTION This invention relates to facsimile printersand more particularly to a printing blade for a facsimile printer of thetype which employs a helical wire on a rotating drum and a bladeparallel to the axis of rotation of the drum for recording anelectrolytic web material passing between the blade and the drum in adirection perpendicular to the axis of the rotating drum.

The most common type of facsimile printer records on electrolytic paperby producing electrical charges across the paper at points where marksare to be made. In a drum-type of facsimile printer, the electrolyticpaper is passed over a drum of nonconducting material around which aconducting wire is wound helically. A blade parallel to the axis of thedrum bears against the drum asthe drum is rotating with the electrolyticpaper passing between the blade and the drum in a directionperpendicular to the axis of the drum. Asthe drum rotates, the helicalwire sweeps across the paper under the blade, thus defining a linevirtually perpendicular to the edges of the paper along which points maybe recorded by selectively energizing the helical wire. Recording isthus accomplished by modulating the energizing signal applied to anelectrical circuit which includes the helical wire and blade. The paperadvances slowly so that successive lines over the entire surface of thepaper are scanned for recording. The electrical charge between the wireand blade causes ions in'the blade to enter the electrolyte of the paperand darken it to thereby mark a point on the paper. Each point isgenerally of almost square shape with sides of about 0.010 in. With drumspeeds on the order of 1,000 RPM, and paper drive speed of about in. perminute, 100 lines are scanned to the inch of paper so that with pointsrecorded of the size indicated, virtually no space is left betweenscanned lines.

The printing blade is electrolytically eroded as points are recorded,and the recording of a long continuous line can result in the formationof a deep groove in the blade. Such a groove may later interfere withproper recording and may tear the paper. One way of preventing theformation of grooves is by forming the blade as a continuous band heldtaut between a roller on one side of the paper and a driven capstan onthe other side of the paper as shown in US. Pat. No. 3,569,987 assignedto Teleautograph Corporation by Kunio A. Sumida. The band is heldinclined to the paper with a sufficient bias force to maintain the edgeof the band against the paper, and with sufficient resilience in theband to compensate for differences in the radius of the helical wirefrom the turning axis of the drum and variations in the thickness of thepaper. The bias force is provided by a leaf spring which contacts theloop belt immediately below its upper edge on the inside of the loop.However, this solution to the electrolytic erosion problem was found tobe unsatisfactory because the continual motion of the rotating band inone direction has a tendency to cut the paper.

Another solution to this electrolytic erosion problem of the printingblade which has been successfully used is to mount a rigid blade on acarrier which is continuously driven with an oscillating motion back andforth across the paper. The rigid blade has been formed of a strip ofmetal bent about 90 down the center along its causing disturbing noiseand non-uniform printing.

Normally, electrolytic printers are as quiet as magnetic tape recorders.

OBJECTS AND SUMMARY OF THE INVENTION One object of the present inventionis to provide an improved printing blade assembly for facsimile printersof the drum type.

Another object is to provide a compliant printing blade fornon-vibrating and silent facsimile printing.

In accordance with the present invention, there is provided for afacsimile printer of the drum type a printing blade apparatus comprisedof a thin strip of resilient metal secured in a carriage along one edge,preferably by a spring-biased eccentric roller. The carriage is mountedon the recorder with the free end of the blade inclined at an acuteangle with electrolytic paper being passed between the printing drum andthe blade. The inclined position of the carriage and blade is adjustedto place the blade against the paper with sufficient force to maintainthe blade on the paper as the drum rotates. The inherent resilience ofthe thin stainless steel blade provides the compliance required tocompensate for variations in the radius of a helical wire wound on thedrum and the thickness of the electrolytic paper. The carriage isprovided with rods which pass through mounting brackets on each end topermit the carriage to beoscillated back and forth in the direction ofthe axis of the rods, thereby moving the blade back and forth on theelectrolytic paper in a direction parallel to the axis of the drum. Thismotion reduces the tendency for electrolytic erosion to notch the edgeof the blade when a long vertical line is printed on the paper.

The novel features that are considered characteristic of this inventionare set forth with particularity in the appended claims. The inventionwill bestbe understood from the following description when read inconjunction With the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial perspective viewof a facsimile printer of the drum type having a printing blade andblade carriage assembly constructed in accordance with the presentinvention.

FIG. 2 is a sectional side elevation of the apparatus taken along a line2-2 of FIG. 1.

FIG. 3 is an enlarged sectional view of the area 33 of FIG. 2.

FIG. 4 is a view in elevation of the blade carriage assembly of FIG. 3.

FIG. 5 is an exploded view of the blade and blade carriage assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a typicalorganization of a facsimile printer of the type which employselectrolytic paper 10 j and a helical wire 11 on a rotating drum 12 tosuccessively scan and mark points on the paper at the points .ofintersection between the helical wire and a metal printing blade 13. Thepaper is stored on a roll 14 ina sealed compartment 15. The paper passesover a guide 16 and out of the compartment through a slitbetween sealingmembers 17 and 18. The sealing member 18 is formed as a thin resilientstrip of metal in order that the slit be closed by pressure of the stripagainst the paper and the rigid sealing member 17. v

The paper passes between the drum l2 and the printing blade 13, and fromthere over a heater not shown to drive'rollers, also not shown. Thedrive rollers pull the paper over the printing drum at a slow speedinches per minute) while the drum rotates at a speed 1,000 RPM)coordinated with the paper speed to produce printed lines substantiallyparallel to the drum axis (100 lines per inch) to virtually fill all ofthespace (assuming points printed with a height of 0.010 inch). Theprinted paper leaving the feed rollers passes between cutting blades(notshown). The blades are actuated to cuteach printed document as it leavesthe feed rollers.

The printing blade 13 is mounted in a carriage 19. The carriage is inturn mounted on the chassis of the recorder by rods 20 and 20 passingthrough blocks 21 and 21 (FIGS. 4 and 5) at each end fastened to thechassis (not shown). Suitable means is provided to adjust the angularposition of the carriage vis-a-vis the paper to maintain a high pressingforce (about 175 grams) of the blade against the paper with an angle ofapproximately between the blade and the paper as shown in FIG. 2.

The blade is typically 9%. inches long, 9/16 inch wide and 0.004 inchthick. The metal selected for the blade is type-302 stainless steel forits qualities of resistance to chemical corrosion and resilience.Type-316 stainless steel would be even more suitable, but at the presenttime is too expensive for the application since the printing blade issubject to wear and must be replaced from time to time. Still other, andperhaps even cheaper, metals may be found with these desired qualities.Consequently, the present invention is not to be construed as beinglimited to stainless steel blades.

A new blade will have an almost square corner along its longitudinaledge bearing against the paper, but after a short burn-in time,thecorner will wear down to present a surface bearing against the paperof 0.010 inch as shown in FIG. 3. The diameter of the wire 11 istypically about 0.032 inch to provide backing for virtually all of thepaper between the wire and the blade to the full height of 0.010 inch.This is so because the paper is sufficiently compressible to cause it toform itself around the wire. The result is that if an electricalpotential is momentarily applied between the printing blade and the wireat any given instant, a point will be printed in the electrolytic paperthat is 0.010 inch high, and virtually 0.010 inch square.

The carriage 19 for the blade is comprised of a long (9 /8 inch) block22 into which set screws 23 pass to secure to the block 22 the rods 20and 20 at the ends thereof. In that manner only the rod ends of thecarriage pass through the mounting blocks 21 and 21 which arecylindrical to permit tilting the block forward with the blade againstthe drum and paper.

The carriage block 22 also has a beveled flange 25. That flange isbeveled to permit the blade to be easily inserted through a slot betweena cover 27 and the flange 25 with a flat side against the beveled sideof the .flange while a spring-biased eccentric locking roller 28 isrotated out of the way by a lever 29 (FIG. 4). Aftc: the blade isseated, the leverof the locking roller is released and a coiled spring30 rotates the locking roller back into the position shown in FIG. 2against the blade. The force of the spring 30 holds the roller againstthe blade withsufficient force to lock it in position. The cover 27 issecured to the block'by screws 31.

FIG. 4 shows in elevation the blade carriage assembl; 19 just described,but as viewed from the front, i.e., from the drum side. FIG. 5 is anexploded view from the other side. The eccentric roller 28 is held inplace for rotation by the lever 29 at one end passing through a hole 32in an end plate 33 secured to the block 22 by screws 34, and by aslotted pin 35 passing through a hole 36 in an end plate 37 secured tothe block 22 by screws 38. The lever 29 and the pin 35'are locked inposition in the ends of the eccentric roller by respective set screws39' and 39. One end of the coiled spring 30 at the center of the coil,is inserted into the slotted pin 35. The other end of the coiled springis wraped around the head of one of the screws'38. When the lever isrotated clockwise, as viewed in FIG. 5, the eccentric locking roller isrotated away from the beveled surface of the flange 25 and the coiledspring is tightened. When the lever 29 is released, the spring rotatesthe eccentric locking roller back against the blade 13, to lock theblade in place. The entire blade carriage assembly 19 is held in aposition near the mounting block 21 by a spring 40 connected between theblock 21 and the carriage block 22.

The rod 20 on the left in FIG. 4 is covered by a plastic cap 41 againstwhich an actuator cam 42 (FIG. 1) pushes to move the rod and carriageblock to the right, as viewed in FIG. 4. The actuator cam is in turnactivated by a drive rod 43 which is driven up and down through a geartrain and an eccentric drive wheel(not shown) by the motor (also notshown) that drives the paper feed rollers. At the downward movement ofthe drive rod43 changes to upward movement, the spring 40 returns therod and the carriage block to the position shown in FIG. 4. In that waythe blade 13 is caused to oscillate back and forth in a path parallel tothe axis of the drum 12 so that while printing one long continuous lineparallel to the edges of the paper 10, there is not a tendency for theapplied voltage to cause electrolytic errosion of the blade at onepoint.

As noted hereinbefore, the blade carriage assembly is rotated to aposition that places the blade against the paper with over a hundredgrams of force. The thin blade is sufficientlyresilient to providedesired compliance of the blade as the drum rotates to allow fordeviation in theradius of the helical wire 11 from the turning axis ofthe drum and the thickness of the paper. That is accomplished byadjusting the position of a pin 44 (FIG. 4) which seats in a yoke 45shown in perspective in FIG. As the pin 44 is moved forward in thedirection of the drum, the blade carriage block 22 is rotated on'therods 20 and 20. The yoke 45 is mounted on a block 46 which is clamped onthe end of the rod 20 by a screw 47. As the blade wears, the bladecarriage block may be further rotated to keep the blade against thepaper with the desired force. Wear of the blade will require thisadjustment not more often than once each day of daily continuous use.

Although particular embodiments of the invention have been described andillustrated herein, it is recognized that modifications and equivalentsmay readily occur to those skilled in the art and consequently, it isintended that the claims be interpreted to cover such modifications andequivalents.

What is claimed is:

1. An improved printing blade apparatus for use in a facsimile printerhaving a rotating drum with a helical conducting wire on the surfacethereof for printing on an electrolytic web that moves over said drum ina direction perpendicular to the axis of rotation of said drum, said webpassing between a blade parallel to said axis and said drum, saidapparatus comprising a thin planar strip of metal held along onelongitudinal end in a position to serve as said blade with an edgeopposite said one end against said web, and

a rigid carriage means for holding said thin planar strip of metal alongsaid one end with said opposite edge against said web and with saidplanar strip inclined at an acute angle with said web, said angle beingselected for said opposite edge to point in the direction of motion ofsaid web wherein said carriage means includes biasing means foradjusting the position of said thin planar strip against said web with adesired pressing force of said strip against said web to maintain saidstrip against said web as said drum rotates, whereby localizedcompliance of said strip is provided to allow for deviations in thediameter of said wire and distance of said wire from said drum axis, andfor variations in the thickness of said web.

2. Apparatus as defined in claim 1 wherein said carriage is comprised ofan elongated block having a longitudinal flat surface inclined at saidangle, said flat surface being in front of said planar strip in respectto the direction of rotation of said drum, and a spring-biased eccentricroller bearing against said surface, whereby said roller may be rotatedaway from said surface to insert said thin planar strip between saidroller and said surface, and then released to hold said strip in placewith the curved surface of said roller behind said strip in respect tothe direction of rotation of said drum to enhance said compliance ofsaid strip.

1. An improved printing blade apparatus for use in a facsimile printerhaving a rotating drum with a helical conducting wire on the surfacethereof for printing on an electrolytic web that moves over said drum ina direction perpendicular to the axis of rotation of said drum, said webpassing between a blade parallel to said axis and said drum, saidapparatus comprIsing a thin planar strip of metal held along onelongitudinal end in a position to serve as said blade with an edgeopposite said one end against said web, and a rigid carriage means forholding said thin planar strip of metal along said one end with saidopposite edge against said web and with said planar strip inclined at anacute angle with said web, said angle being selected for said oppositeedge to point in the direction of motion of said web wherein saidcarriage means includes biasing means for adjusting the position of saidthin planar strip against said web with a desired pressing force of saidstrip against said web to maintain said strip against said web as saiddrum rotates, whereby localized compliance of said strip is provided toallow for deviations in the diameter of said wire and distance of saidwire from said drum axis, and for variations in the thickness of saidweb.
 2. Apparatus as defined in claim 1 wherein said carriage iscomprised of an elongated block having a longitudinal flat surfaceinclined at said angle, said flat surface being in front of said planarstrip in respect to the direction of rotation of said drum, and aspring-biased eccentric roller bearing against said surface, wherebysaid roller may be rotated away from said surface to insert said thinplanar strip between said roller and said surface, and then released tohold said strip in place with the curved surface of said roller behindsaid strip in respect to the direction of rotation of said drum toenhance said compliance of said strip.